1. Technical Field
The present disclosure relates to auto-focus (AF) techniques and, particularly, to an AF system which can determine correct focus even in dim light conditions and an AF method thereof.
2. Description of the Related Art
Digital cameras typically include an AF system to automatically focus on an object. AF systems generally include an active AF and a passive AF system. The active AF system measures distance to the object using an individual measuring system and adjusts the digital cameras for correct focus. The passive AF system determines correct focus by performing passive analysis of images of the object, which is mainly achieved by contrast measurement technique. The contrast measurement technique assumes that the intensity difference between adjacent pixels of the images naturally increases with correct focus and adjusts the digital cameras for correct focus based upon contrast values measured from the images. Commonly, focus accuracy of the active AF system is less than that of the passive AF system. However, the active AF system may also fail to focus properly on an object that is very close to the digital camera. The passive AF system also may focus improperly when contrast in the images is low, notably with monochromatic views or in low-light conditions.
Therefore, it is desirable to provide an AF system and an AF method thereof, which can overcome the above-mentioned problems.